I think a more interesting question, to help understand how capitalism and free markets can work, is "Why did slavery end?" After all, throughout all of recorded history there was always slavery, but something happened in the 1800s that made people want freedom for more individuals than ever before. I also believe that part of the reason for an ending of slavery was the fact that the leading nation in the world (at that time), Great Britain, who was also a leader in ending slavery, just happened to be the country where free trade and capitalism flourished the most.

add "the free market freed the slaves" to the list of demonstrably wrong statements presented as if they are facts